Art of wood distillation.



H. 0. CHUTE.

ART OF WOOD DISTILLA'HON. APPLICATION FILED MAY 23. m0. RENEWED MAY19,1917.

Patented D0018, 1917.

destructively distilling UNITED STATES, PATENT OFFICE.

HARRY 0. OEU'IE, 0! NEW YORK, N. Y., ASSIGNOR TO K. P. HoELBOY, OFWASHINGTON,

\ DISTRICT OF COLUMBIA.

Specification of Letters Patent.

Patented Dec. 18, 191 '7'.

Application filed Kay 28, 1810, Serial 110. 588,004; Renewed Kay 19,1917. Serial No. 189,780.

7 k To all whom it may concern."

Be it known that I, HARRY 0. Cum, a citizen'of the United Sfiates,residing at-New York, in the county of New York and State of New York,have invented certain new and useful Improvements in the Art of WoodDistillation, of 'which the following is a specification. v

This invention relates to the art'of wood distillation; and it comprisesa method of wood and regaining the by-products there rom wherein wood orother vegetable material is destructively dis- 'tilled in retorts underconstant pressure, said pressure being controlled independently of theamount of incondensable gaseous products formed, the gaseous effluentfrom the distillation is passed through a temperature- ,controlledchannel to regulate its tempera 20 ture, is then systematically washedand purified by a countercurrent of tarry or oily bodies, is then freedof its acetic acid by neutralization with a body of alkaline materialmaintained at a comparatively high temperature to form an acetatesolution and is thereafter treated to regain wood spirit, said woodspirit being subsequently purified; and it also comprises an assemblageor organization of apparatus elements comprising a retort, means forwithdrawing efliuent vapors therefrom and controlling the pressuretherein, a temperature-regulating device receiving the efiiuent' gases,means for distilling tar, means for systematically scrubbing theefiiuent gases with the distillate obtained, means for recoverin theacetic acid from the purified gases in t e form of a concentratedacetate solution, means for thereafter recovering wood spirit, means forpurifying said wood spirit, and means for withdrawing incondensablegases, said means being connected to said pressure controlling means;all as more fully hereinafter set forth and as claimed. a

In the destructive distillation of wood and the like, the productsobtained are many and of varied nature, but for the present purposesthey may be regarded as consisting mainly of permanent gases, water,wood spirit, acetic acid, hydrocarbons, tar oils, keytones, and tar. Thewood spirit is a mixture consisting for the most part of methyl alcoholand acetone with some methyl acetone and methyl acetate. The tar and taroils are complicated mixtures of hydrocartilled being bons, phenols,aldehydes, esters and less known tarry and oily bodies.

In, this country the distillation is ordi-' narily erformed inexternally heated retorts, t e kiln processes in which air is drawnthrough the mass of wood to be disess frequently used. The

torts employed are often very large, some times reaching 45 and 50 feetin length. Into these long retorts the wood is frequently run on cars.The'nature of the product obtained in wood distillation dependsconsiderably upon the pressure prevailing within the retort and with aretort of any slze it is diflicult to control this pres sure. The gasesand vapors distilled from the wood do not come ofl evenly but indifferent amounts at different times. It is, furthermore, difiicult toprevent leaks in the retort, and for this reason it is as a rulebetproducts of wood distillation, the distillate is cooled and condensedas a whole, the permanent gases alone remaining uncondensed. Thedistillate from hard woods on standing separates into two layers; onebeing tar containing more or less acid and wood spirit, and the otherbeing crude pyroligneous acid. The pyroligneous acid contains the aceticand other acids and the wood spirit together with tarry and oily bodiesin solution and suspension. It 1s always separated gravitally from thetar as cleanly as possible, but it nevertheless always still contains aconsiderable quantity of impurities.

The principal problem in the art of wood distillation is that ofrecovering the main valuable products, the wood spirit and the aceticacid in as pure 'a state as possible with the minimum of manipulationand labor and fuel. The acetic acid is always recovered as an acetate;generally as acetate of lime. A

In this recovery the main difliculty is in eliminating the tar and tarrybodies which are found to be separated at every step. With the variednature of the components of the tar, some of the constituents are apt togo forward and contaminate all the products whatever method of recoverybe adopted. One method of recovery much used is to distil the acid as awhole, leaving much of the contained tar behind in the retort. Thedistillate on neutralization yields an impure alcoholic distillateneeding much rectification and purification before it can be made amerchantable article. After removing the wood spirit, the water isevaporated ofi', leaving gray acetate; gray acetate of lime, forexample. Another method is to neutralize the whole mass of pyroligneousacid, distil oif the alcohol from the neutralized liquid as before andthen evaporate down to obtain brown acetate. This yields a very impureacetate and an equally impure wood spirit; the latter, under thecircumstances, containing foul smelling amins. A better method now muchused is to perform a systematic distillation, first distilling oil afraction of the pyroligneous acid to obtain a midstrength acid alcoholicdistillate running between 10 and 25 per cent. apparent alcoholicstrength. Under the laws governing the distillation of immisciblefiuids, in the distillation much of the tarry and oily matter insolublein a distillate of this character goes forward with the distillate andon allowing it to stand can be settled out. On now neutralizing theliquid or making it alkaline, a further amount of impurities may beseparated and settled out; an excess of alkali appearing to resinify thesoluble impurities or some of them and to cause a separation. After thesecond separation, the alcohol may now be redistilled to make amerchantable article freely miscible with water. The acid remaining inthe still after distilling off the acid alcohol is now purer, thealcohol having carried over a considerable amount of the impurity, andit can be distilled to give an acid of much purer nature, thenon-volatile tars remaining behind in the still. Preferably in thissecond distillation the acid vapors are condensed in the heatingchambers of a multiple effect apparatus used to evaporate the acetatesolution formed by neutralizing such condensed acid.

The present method is in line with that just described in that itmethodically removes as much of the impurities at each stage aspossible. It comprises obtaining the original distillate from the woodof more uniform composition by regulating the pressure in the retort,methodically'lowering the temperature of the products of destructivedistillation somewhat to condense out part of the tar and thensystematically scrubbing the gases, which are still hot and above thecondensing point of either acid or alcohol, with a countercurrent ofdistilled oils from tar. In the gaseous product leaving the still, atall moderate temperatures probably much of the true tar is not in astate of vapor but is liquid, being in the form of fine droplets orparticles entrained and carried forward by the rushing current of gases.By contacting with a washing or scrubbing body of oil, most of thesesuspended particles can be removed while the scrubbing oil alsodissolves and retains more volatile oily and tarry sub stances, so thatthe body of gases and vapors is also still further purified by a truesolvent action. This body of wash oil is best obtained by a methodicaldistillation of the tar recovered from the operation itself.

In the scrubbing operation preferably the temperature of the gases undertreatment is maintained at as low a point as possible without reachingthe condensing point of pyroligneous acid, both because more of thevolatile components of tar can be condensed and dissolved out the lowerthe temperature is and because at a comparatively low temperature, justabove the boiling point of pyroligneous acid, the scrubbing can beeffected in efiicient countercurrent apparatus of the nature of a columnstill without danger of twisting and warping it; a serious matter whenthe still is made of copper. Copper is the best material to employ, bothbecause it is freely heat conductive, therefore allowing an efficientstill action, and because it is not attacked by acetic acid or the taracids as is iron. The temperature of the gases bein scrubbed shouldhowever be substantially a ove the condensing point of the pyroligneousacid.

Operating in this manner, the gases going to and through the scrubbingapparatus are somewhat above 100 C. and they can next be passed throughor against a body of alkali, such as milk of lime, in a countercurrentapparatus and the acetic acid condensed out as a body of concentratedacetate solution, merely enough water condensing to dissolve thisacetate. Owing to the eflicient preliminary scrubbing, this acetatesolution will be fairly pure and may be directly concentrated to obtainthe 8:2 per cent. acetate. It is obviously better, once having the waterof the products of destructive distillation in the form of vapor tomaintain it as such, condensing out merely the acid rather thancondensing both water and acid and subsequently re-evaporating thewater.

Under the conditions described, while the acetic acid condenses, thealcohol and the bulk of the water go forward. They may next be condensedtogether by any suitable condenser, giving a weak alcoholic distillate;Strong alcohol may be directly distilled from this condensate andafterward rectified to give a pure article; It is however better todistil the condensate to obtain -a. midstrength article between and 25per cent. apparent alcohol content as tested by.

the alcoholometer and purify it prior tomaking the stronger alcohol.This midstrength distillate will be neutral, the alcohol vapors havingpassed through lime. From this neutral distillate some oil will separateand this should be removed. On weakly acidifying with a little aceticacid, a further separation of impurities can be attained, the liquid nowbeing made of the character of that obtained by the direct distillationof pyroli ieous acid to obtain the midstrength acid distillate in theprior rocess hereafter described. After the acidi cation the liquid maybe again neutralized, or, and better, made alkaline with an alkali, suchas lime.

In the presence of this alkali a further' water without separationofimpurities or,

what is termed in the trade, a non-mllking alcohol.

After the condensation of the alcohol and 'water as described theincondensable gases can be removed and may be utilized for heating theretorts, being combustible in character. In removing these incondensablegases they may be taken out through a suction fan. This suction fanproduces a suction throughout the entire system extending to the retortand its action may be controlled by the evolution of gas in-the retort,the gases and vapors coming from'the retort being passed into,a gasbell. In the scrubbing operation the .character of the oil used as awash oil is not a matter of indiflerence The best effects are obtainedby using a. certain fraction of the oils distilled from the tarrecovered in the operation itself.

In a typical and complete installation under the present process, thegases coming from the retort may be passed through a cooled conduit. Inthis conduit a large part of the tar separates and accumulates. From theconduit the gases may be passed into a bell floating in a bath of tarand tar oils. From this bell the ases may be taken by a conduitandcausef to bubble through tar or tar oils. In this scrubbing treatmentthe temperature should be maintained at a temperature above thecondensing point of the pyroligneous acid which is, of course, alsoabove the condensing temperature of water or wood spirit. From the oilscrubbing operation the gases may next be led through an apparatuswherein they may be scrubbed with an alkaline liquid at a temperatureappropriate to form acetate solution without condensing the alcohol andwater. From this neutralizing scrubbing the gases and vapors may be ledto a condenser, alcohol and water condensed out and the remainingincondensable gases led past a valve by a suction-fan, the valve beingconnected to the gas bell and regulated thereby.

In the accompanyin illustration I have shown, more or lessiagrammatically, an assemblage of apparatus elements within the presentinvention and useful in rforming the described processes. In this sibwing the figure represents a view partly in vertical section andpartly in elevation of a complete installation. Element 1 is a retort,shown as of the long horizontal type heated by fire lines 2. This retortis inclosed in the brick chamber (shown broken away) 3. Tapping theretort at a plurality of points are outlets 4, communicating with a gas.and vapor main 5, lying in a temperature controlling casing 6. Thetemperature within this casing may be kept constant by sprinkling theconduit with water from suitable means (not shown), or by maintainin abath of high boiling liquid, such as a so ution of calcium chlorid,within the casing. Tapping the conduit at its lowest point is a valvedpipe 7 leading to a tar still. From an upper point in the conduit leadspipe 8 ending beneath a gas bell 9. This gas bell plays within a housing10 containing a bath of tar or other liquid 11. Also ending within thegas bell is a conduit 12, carrying an overflow device 13 consisting of apipe sealed by a cup, whereby the excess of the accumulating tar may betapped into this conduit. This overflow device 13 comprises a curvedpipe, the upper end communicating with the interior of gas bell 9through the orifice in the periphery of conduit '12 while the lower endcommunicates with the interior of conduit 12. When the level of the bathin housing 10 and bell 9 rises beyond this orifice, the excess of tarflows through pipe 13 into conduit 12. This conduit 12 takes vapors andgases and overflowing tar from tanklO into a scrubbing device 14. Thelower end of the conduit may be serrated as at 15 and raised from thefloor of this apparatus, which is of the well known countercurrent typeand in structure is much like a column still carrying shelves andinverted cups 16, and overflows 17. It is provided with means 18 and 19for delivering tar oils to the upper shelves. At its upper end conduit20 takes the scrubbed gases and vapors through another scrubber 21,which also serves as a temperature regulator and pans go through conduit24 into a nontralizer 25. This neutralizer is also of the w ell knowncountercurrent type and has the general internal construction oi acolumn still, being provided with cups and lates or like devices.Alkali, such as milk 01: lime, is fed into it through pipe 26, from tank26, and neutralized liquid is removed through valved pipe 27 to dryingpan 27. The temperature of this apparatus (25) is kept at such a pointthat acetic acid Wlll condense or be absorbed and form a strong solutionof acetate while the main body of the alcohol and water remainuncondensed and go forward. The uncondensed gases and vapors leave theneutralizer through pipe 27 leading to condenser 28, which is of anordinary type. From the condenser, the condensed alcohol and water areremoved by sealed pipe 29 while uncondensed gases go through pipe 30,past valve 31, to suction device 32 and thence to a point of use. Thevalve is provided with counterbalanced weight 33 and cord 34 connectedto the top of the gas bell. The valve being thus connected wlth the gasbell, when the gases flow from the retort and fill the bell its risingopens the valve through the cord connection, whereby the fan or othersuction device used automatically draws the gases through the mechanismin the direct ratio of their formation. The suction device may be run atconstant speed by any form of motor. The condensed water and wood spiritor alcohol pass from the condenser into the holding tank 35, and thencethrough pipe 36, pump 37 pipe 37 heat exchanger 37 and pipe 37, to thecontinuous refining still 38 where it is brought to the form of amid-strength alcoholic distillate of between 10 and 25 per cent. ofapparent alcoholic content. Tester 38 allows control of the operation ofthe still. This distillate goes through condenser 39 and trybox 40, andpasses into the settlin tub 41 provided with valved outlets 42 an 43 atdifferent heights, through which settled oily impurities may be removed.It may be advisable to acidity the contents of the settler to promoteseparation of oils or this may be done in a separate vessel. Valvedoutlet 44 serves to draw off the aqueous 1a er or dilute wood spirit totank 45, provi ed with stirrer 46, wherein the liquid is mixed withanalkali, preferably lime. The amount of admixture may be merelysufiicient to bring the liquid to neutrality but preferably is enough tomake it alkaline. Alkalinity by causing a resinification andpolymerization of impurities, promotes purification. The impuritiesseparated may be deposited in this tank. The liquid is decanted throughthe pipe 47 and is again passed through the fractionating continuousstill 38 which now acts as a secondary still when a distillate of morethan 82 per cent. alcoholic content and perplace 52, perforated steampipe 53, condenser 54, and valved pipe 55, and by its means the tar maybe separated into fractions of different boiling point and of differentnatures in the presence or absence of steam or water vapor. Thesedifferent condensates may be led into separate tanks 56 and 57.

In operating the apparatus the cord wood is placed in cars of iron orsteel and shoved into the retort 1 and a fire is built in fireplace 2which is arched over to allow of even distribution of the heat to theretort. The gases emerge through the pipes 4 as soon as a carbonizingtemperature is reached in the retort and pass through thetemperature-regulating device 6 where they are cooled as low as possiblewithout condensing water or acids. Thence the gases and vapors pass tothe bell 9. This is so weighted that it moves up and down according tothe predetermined pressure it is fixed to carry and in so doing it opensthe valve 31 through the cord mechanism 34 as the bell rises. Thisallows the suction fan 32 to form a partial vacuum which serves towithdraw the gas from 9 as rapidly-as it enters. In this bell there isalways an accumulation of tarry and liquid matter forming and serving asa seal. The excess of tar passes out through the orifice 13 and followsthe gas which passes through 12 to the scrubber 14 which as a layer oftar oils on each plate and on the bottom. In passing into this apparatusthe gases escape as small bubbles past the serrated edge of the conduit12 and thus bubble through the layer of tar oils in the botom of 14.Passing up through the scrubber .the process is repeated in each higherchamber in the well known way; this manner of passing a gas against a.countercurrent of liquid being used in many industries, such as inmaking illuminating gas, the soealled ammonia soda process, thefractional distilling process and others. When the gas reaches the topof the first scrubber, it is passed through the other combinedscrubbing, cooling and temperature controlling arrangement which is aseries of pans arranged to pass the gas in a tortuous manner sivelycooler surfaces. This apparatus is of the type known in the wooddistilling art as Burcey "pans. The tar oils flow through 20.

i into 14. The composition of the liquid which flows in thecountercurrent and which serves to scrub the gas is of some importance.The best scrubbing fluid is produced by distilling and separatin thevarious oily fractions of the tars WhlCh have been produced in theprevious operation. The tar which settlessteam is shut'ofi'and the fireis increased in the fireplace 52 to a point where other tar oils not 5cially volatilewith steam are evolved. hese latter taroils are led-intothe tank 57 and kept separate fromthe steam volatile oils which havebeen run into 7 tank 56 and which are useful for other purposes, but arenot desirable as washing oils this process. These oils in. 57 which aresubstantially non-volatile .in steam are pumped in a continuous streamvby pump 19 into the top of the-scrubber 14 through 18 or'into andthrough the top Burcey pan 23 through the pipes 18. These oils haveseveral functions in the scrubbers, firstly, to absorb the tar and oilsin these gases and, secondly, to keep the tar in them liquid bdissolving the hard tar which otherwlse w' 1 form in and clog theapparatus. Another function is that of cooling the vapors to the desiredpoint. These scrubbing oils must be liquid at the working temperaturewhile not particularly volatile with the water va or contained in thegases from the retorts. hey must also serve to absorb and remove as muchas possible of those steamvolatile oils which are always present.

Steam volatile oils should therefore be fractionated away from thecollected body of tar and the oils not particularly volatile with steamused for washing as described, As these washing oils continuously returnto the tar still, it is only necessary to use a fraction of them in thecirculation and the remainder can from time to time be removed from thecirculation and otherwise disposed of. The gas and vapor passing fromthis scrubbing operation are freed to a great extent from the impuritieswhich would otherwise contaminate the desired final products, acetatesand alcohol. The vapors freed from tar and containing all the volatileacids together with the water and wood spirit pass from the scrubbers 14and 20 through 24 into the absorbing appara tus 25 which is a'countercur'rent apparatus simi-' lar to the scrubber 14'. But in thisabsorber the vapors meet a countercurrent of alkali, as milkof lime,which enters from the storage tank 26", through valved pipe 26 whichallows a regulated feed of alkali in amount sufficient to neutralize.theacids. The vapors meet a progressively stronger alkali solution orsuspension as they rise'through the higher chambers, which serves toremove all the.

acid while allowing thewater and other volatile constituents to pass on.While, it might bepossible to condense out-the water from thegasescoming from this operation at a temperature which would allow astronger alcohol to'. pass on for a later condensation,

yet I: prefer to cool the gases immediately to as low a temperature aspossible after the acids have been removed," condensing both dilutesolution of alcohol inwater. Thls is alcohol and water and thus obtainmga done in condenser 28 and as the yield of aqueous products from a cordof wood by destructive distillation is about 220 gallons while the.yield of alcohol seldom exceeds ten gallons and as practically all thewater and alcohol are in thisdistillate, thealc'oholic content willalways be below five per cent. This condensate still cont-ainsmany ofthe volatile impurities of the ordinary pyroligneous distillates andIproceed to recover the alcohol therefrom and purify it by a methodicalsystem of fractional dis-- tillations and chemical treatments. I firstpump the weak liquor from 35 into the still.

38 and produce a distillate of between. 10

per cent. and 25 per cent. alcoholic contents,

.ing an acid or both. I find these distillates when of acid natureseparate the oils better than when neutral or alkaline; In some cases,the oils will rise to the top, in some other cases they settle to thebottom, and in still other cases they .are found at both top and bottom.In any case these oils may be removed through the draw-ofl cocks 42 and43. The aqueous liquid is drawn into tank 45 and an alkali, preferablymilk of lime, is added in such excessthat a reaction occurs producing ayellow color. The reaction usually forms a deposit which settles to thebottom of the tankfrom which the liquid may be removed; but whether thisdeposit forms or does not, some impurities which were formerly volatileare rendered non-volatile. By this methodical treatment 1t 1s possibleto obtain a llquid such that if it tion of water in any proportlon itremainsv perfectly miscible therewith. This is the and high standard for82 per cent. crude alcohol and the roduct may therefore be run directlyinto arrels for shipment or further treated to produce refined alcoholof 95 per cent. strengths for conbumption in the arts: While forconvenience of illustration I show all the apparatus for the recovery ofthe valuable by-products as connected to a single retort, I prefer tohave some of the apparatus treating in common the product from an entireset of a plurality of retorts. I prefer to have the firsttemperature-regulating device, the as hell, the scrubbers, the aceticacid absorbers and the water and wood spirit condensers separate foreach retort, as each of these pleces of apparatus must be regulatedaccording to the working of the individual retort, but the tar distillinand circulating apparatus and the alcohol stills, the gas exhausters andltmetub may with advantage work on the common products of all theretorts. This simplifies the plant by requiring only one set of thelatter apparatus for each plant. In this case it is well to specializethe apparatus somewhat further. For example, all the tar conduits maylead to a single set of containers, and a pair of tar stills may beused, the still for removing the steam-volatile part of the tar being aseparate s'till. .It may be of different construction from that in whichthe nonsteam-volatile part is removed. The steaming still may be awooden still with steam heating coils in addition. to the perforateddirect steam coils. The boiling still may then be of iron, fire heated.The condensed tar from the scrubbers will hold considerable acid in itand this acid may be distilled out of the tar and passed through thescrubber with the scrubbing oils. In this case the entering gases in thescrubber may be hotter, the heat being absorbed in vaporizing the acidso introduced. When the alcohol plant is built for a plurality ofretorts it is better to have two stills for the two distillations of thealcohol though I have used both systems with one and with two stills,and find both satisfactory. With two stills the secondary one fortreating the 10-25 per cent. distillate may be constructed on theso-called French system roducing refined 95 per cent. alcohol direct seeU. S. Patents 436,764 and 436,684). I prefer however to produce 82 percent. by the continuous process and then re-distil in the ordinarykettle and column apparatus as this allows of introducing a small amountof fixed acid, such as sulfuric, to the 82 per cent. alcohol beforedistillation to retain any amins or other alkaline volatile compounds.It is not desirable to add this acid to the 10-25 per cent. prod- 1 notas it is too impure and the acid would react with the impurities. Inabsorbing the acld from the gases the lime milk may be diluted to apoint which will supply enough water to allow of the solution of theacetate formed. The reaction is exothermic and I find on experiment thatif a strong milk of lime is added to absorb the acid that the solutioncrystallizes in the apparatus. Another way of controlling the strengthof the acetate solution is to add water directly to the top of theabsorber till the solution running into the evaporating pan 27 is of there uired density.

at I claim is:

1. In the art of wood distillation, the process which comprises leadingvapors from a wood distilling retort directly from said retort through acooling and temperature-regulating device and cooling said vaporstherein to a temperature above the condensing point of the volatile acidcontained in sa1d vapors and passing said vapors against a current ofseparately distilled tar oils to remove tar.and separately distillingsaid tar to produce said tar oils as a fraction.

2. In the art of wood distillation, the

rocess Which comprises leading vapors rom a wood distilling retort intoa governing reservoir and withdrawing said vapors from said retort intosaid reservoir at a rate proportional to the speed of the generation ofsaid vapors.

3. In the art of wood distillation, the process which comprisespre-cooling va ors from a wood distilling retort and was ing the.pre-cooled va ors in a countercurrent of a separately distillednon-steam-volatile distillate from liquid tar.

4. In the art of wood distillation, the process which comprisesgenerating acid vapors in a wood distilling retort, scrubbing saidvapors with a tar oil fraction and absorbing the acid from the scrubbedvapors by a countercurrent of alkali.

5. In the art of wood distillation, the process which comprisesproducing vapors in a wood distilling retort, scrubbing the vapors witha tar oil fraction, absorbing the acld from the scrubbed vapors,condensing water and wood spirit together from the vapors, distillingthe condensate to between .10 and 25 per cent. alcohol, acidifying thedistillate, separating out the oily impurities rendering the residualalcoholic liquid neutral or alkaline and reseparating.

7. In the art of wood distillation, the process which comprisesproducing vapors in a wood distilling retort, separating'the tar,fractionatin out a tar oil fraction from said tar and scru bing saidvapors with said volatile oils.

8. In the art of wood distillation, the process which comprisesproducingvapors ln a wood distilling retort, separating the tar,fractionating out tar oils not vo atile with steam from said'tar andscrubbing said vapors with said non-volatile oils.

9. In the art of wood distillation, the

process which comprises distilling wood in a retort under constantpressure, cooling the resultant vapors to a temperature near a directratio to the speed of generation of such vapors and gases, and means forcooling the removed gases to a temperature above the boiling point ofpyroligneous acid andremoving tar from cooled gases.

11. In the art of wood distillation, an apparatus comprising a wooddistilling retort having a vapor exit, a pre-cooling conduitcommunicating with said vapor exit, -a scrubbing apparatus communicatingwith said conduit and means for feeding said scrubber with tar oils.

12. In the art of wood distillation, an apparatus comprising a wooddistilling retort having a vapor exit, a pre-cooling conduitcommunicating with said vapor exit, a scrubbing apparatus communicatingwith said conduit and means for feeding said scrubber with tar oils,there being pressureregulating means interposed between said retort andsaid scrubbing apparatus.

13. In the art of wood distillation, an apparatus comprising a wooddistilling retort having a vapor exit, a pre-cooling conduit connectedto said orifice, a pressure-regulating bell into which said conduitopens, means for scrubbing and condensing condensible portions of vaporsbeyond ,said bell, means for producing suction throughout the system andmeans for regulating said suction controlled by said bell.

14. In the art of wood distillation, an apparatus comprising a wooddistilling retort having a vapor exit, means for carrying vapors throughsaid exit into an adjustable float, a casing containing said float, acon duit beyond said float, means for roducing diminished pressurewithin sald conduit and means for regulatlng said pressure,

the float being so connected with the regulating means that on risingthe regu-- latmg means open .and vapors are drawn through the system inproportlon to-the speed of generation.

In the art of wood distillation, paratus comprising a wood distillinretort, a gas cooler taking vapors there rom, a pressure regulatorconnected to the cooler,

an apja scrubber beyond the pressure regulator and atemperature-controlling devlce be yond the scrubber, saidtemperature-controlling device having. means for passing vapors throughprogressively cooler spaces.

16. In the art of Wood distillation, an apparatus comprising a wooddistilling retort, a gas cooler taking vapors therefrom, a pressureregulator connected to the cooler, a scrubber beyond the pressureregulator and a temperature-controlling device beyond the scrubber, saidtemperature-controlling device having means for passing vapors throughprogressively cooler spaces and means for passing the vapors therefromthrough a chamber containing alkali.

17. -'In the art of wood distillation, an

apparatus comprising means for destructively distilling wood, means forscrubbing the products of'said destructive distillation in acountercurrent of tar oils not volatile with steam and means forfractionating tar to produce said oils. 18. In the art ofwooddistillation, an apparatus comprising means for destructivelydistilling wood, means for scrubbin the products of said destructivedistillation with tar oils not volatile with steam, means forfractionating tar to produce said oils and means for producing acontinuous flow of said oils through the scrubbing means.

19. In the art of 'wood distillation, an apparatus comprising means fordestructively distilling wood, means for pre-cooling the vapors, meansfor separating tar, means for fractionally distilling said tar and meansfor scrubbing the gas with a fraction of the distillate from the tar.

20. In the art of wood distillation, the process which comprisesgenerating acid vapors in a wood distilling retort, scrubbin said vaporswitha tar oil fraction and absorbingthe acid from the scrubbed vapors bya countercurrent of alkali.

21. In the art of wood distillation, the process which comprisesproducing vapors in a wood distilling retort, scrubbing the vapors withtar oils, absorbing the acid from the scrubbed vapors, condensing waterand wood spirit together from the vapors, distilling the condensate tobetween 10 and per cent. alcohol, acidifying the distillate, andseparating out the oily impurities.

22. In the art of wood distillation, the process which comprisesproducing vapors in a wood distilling retort, scrubbing the vapors withtar oils, absorbing the acid from the scrubbed vapors, condensing waterand wood spirit together from the vapors, distilling the-condensate tobetween 10 and 25 per cent. alcohol, acidifying the distillate,separating out the oily impurities rendering the residual alcoholicliquid neutral or alkaline and reseparating.

23. In the art of wood distillation, the process which comprisesproducin vapors in a wood distilling retort, scrub ing the vapors with atar oil fraction, absorbing the acid from the scrubbed vapors,condensing water and wood spirit together from the vapors, anddistilling the condensate to between 10 and 25 per cent. alcohol.

24. In the art ofwood distillation, the process which comprisesdistilling wood, maintaining the distillation pressure substantiallyconstant by withdrawing the evolved vapors at a rate proportional to thespeed of their formation, and passing said vapors in contact with a taroil fraction liquid at the temperature of operation and non-volatile insteam.

25. In the art of wood distillation, the process which comprisesdistilling wood, maintaining the distillation pressure substantiallyconstant by withdrawing the evolved vapors at a rate proportional to thespeed of their formation and leading said.

vapors against a countercurrent of tar oils.

26. In the art of wood distillation, the process which comprisesdistilling wood, maintaining the distillation pressure substantiallyconstant by withdrawing the evolved vapors at a rate proportional to thespeed of their formation, and scrubbing said vapors by passing them 1ncontact with a liquid consisting of the high boiling fractions of thedistillate from wood tar.

27. In the art of wood distillation, the process which comprisesproducing vapors in a wood distilling retort, withdrawing said vapors ata rate varying directly with the speed at which the vapors are evolved,cooling the vapors, preparing a high boiling oil fraction by distillingwood tar and scrubhing the cooled vapors therewith.

28. In the art of wood distillation, the process which comprisesproducing vapors in a wood distilling retort maintaining substantiallyatmospheric pressure in the retort by withdrawing the product ofdistillation at a variable rate corresponding approximately to thevariable speed of vapor evolution, cooling the vapors to a temperaturesomewhat above the boiling point of pyroligneous acid, scrubbing saidvapors with a countercurrent of separately distilled tar oils, andfractionating back to the scrubber a portion of liquid condensed fromthe vapors to provide temperature regulation in the scrubber.

29. In the art of wood distillation, the

of removal ,0

30. In the art of wood distillation, the

rocess which comprises pro-cooling vapors rom a wood distillin retort toa temperature just above the bo1 ing point of pyroligneous acid, washingthe pro-cooled vapors with the high boiling fractions of wood tardistillate, absorbing the acids from the purified vapor by hot alkalisolution, condensing the remaining alcohol and water in the gases,removing the tgases and controlling the speed the gases to maintainatmospheric pressure on the retort.

31. In the art of wood distillation, the process which comprisesdistilling wood in a retort at atmospheric pressure, cooling theresultant vapors, allowing part of the tar in the vapors to separate bydeposition, and passing the partially detarred vapors against acountercurrent of high boiling tar 01 s.

32. In the art of wood distillation, the process which comprisesseparating tar from the vapors generated in a wood distillin re-' tort,fractionating the high boiling oils rom the tar so separated, andreturning the high boiling oils into contact with said vapors to aid inseparating the tar.

33. In the art of wood distillation, the process which comprisesseparating impurities contained in the vapors generated in a wooddistilling retort, isolating certain constituents from the impurities soremoved, and employing such isolated constituents in the treatment ofthe pyroligneous vapors.

34. In the art of wood distillation, the process which comprisesproducing vapors in a wood distilling retort and purifying said vaporsby passing them in contact with a 1countercurrent of separatelydistilled tar 01 s.

35. In the 'art of wood distillation, an apparatus comprising a retort,a pre-cooler connected thereto and a regulating bell receiving vaporsand gases from said precooler, suction means for controlling passage ofgases and vapors and connecting means between said regulating bell andsaid suction means.

36. In the art of wood distillation, an apparatus comprising a retorthaving a vapor exit, a floatable bell in unobstructed communication withsaid exit, vapor treating means beyond said bell, suction means beyondsaid vapor treating means and means for controlling said suction meansby the fluctuations of said bell.

37 In the art of wood distillation, the process whichcomprises producingvapors in a retort under atmospheric pressure and scrubbing the vaporswith a countercurrent of high boiling oils fractionated from wood tar,said scrubbing being performed in two stages, the latter stage of saidscrubbing bein performed under cooling conditions ermlttmg a limitedreflux of condensates into the earlier stage to give temperature controlof such earlier stage.

38. In the manufacture of wood alcohol, the process which comprisesproducing a neutral alcoholic distillate of a strength between 10 andper cent., acidifying the same to per mit separation of impurities,removing the separated impurities, adding alkali to separate furtherimpurities and re-distilling to produce a miscible alcohol 0;" 80 percent. or stronger.

39. In the art of wood distillation, an apparatus comprising a retort, apositively precooling conduit with means for withdrawing tar depositsand a pressure regulating bell in open connection and in combinationwith an apparatus for scrubbing gas by a counter current of separatelydistilled tar oils.

40. In the art of wood distillation, the process which comprises leadingvapors directly from a retort through a cooling andtemperatlire-regulating device and cooling said vapors therein to atemperature above the condensing point of the volatile acid contained insaid vapors, separating tar from said vapors, separately distilling saidtar and scrubbing said vapors with a tar oil fraction from thedistilling operation.

41. In the art of wood distillation, an apparatus comprising a retort, apositively precoolin conduit, means for passing vapors from tie conduitagainst a counter current of tar oils, means for passing the vaporsagainst a counter current of alkali, a condenser, and means forproducing a variable suction governed by the flow of vapors from theretort, all in vapor connection.

42. The process of removing steam-volatile oils from pyroligneous acidvapors which comprises scrubbing said vapors with a counter-current oftar oils substantially free from steam-volatile oils.

43. In the art of wood distillation, the process which consists ingenerating vapors in a retort, sucking said vapor through a countercurrent of tar oils to remove impurities and maintaining the vapors inthe retort at atmospheric pressure.

44. In the art of wood distillation, the process which comprisesdistilling wood, maintaining the distillation pressure subtantiallyconstant by withdrawing the evolved vapors at a rate proportional to thespeed of their formation, cooling said vapors to a temperature above thecondensing point of volatile acids contained therein, and scrubbing saidvapors with a counter our- 7 rent of separately distilled tar oils.

evolved vapors at a rate proportional to the speed of their formation,coolin said vapors to a temperature above the con enslng point 0fvolatile acids contained therein, scrubbing a said vapors wlth a countercurrent of separately distilled tar oils, fractionatin back to thescrubber a. portion of liqui condensed from the vapors to providetemperature regulation'in the scrubber and absorbing the acid from thescrubbed vapors by passing said vapors against a counter current of hotalkali solution.

46. In the art of wood distillation, an apparatus comprising a retorthaving a vapor exit, a fioatable bell in unobstructed communication withsaid exit, a device arranged for scrubbing vapors by a counter currentof tar oils, suction means beyond said scrubbing device and means forcontrolling said suction means by the fluctuations of said bell.

47. In a wood distillation apparatus a device comprising means forscrubbing vapors with a counter current of tar oil, and means forsubsequently condensing a high boiling fraction from said vapors andreturning it to the scrubber to control temperatures therein.

48. In the art of wood distillation, the process which comprisesproducing vapors in a retort, scrubbing the vapors with acounter-current of high boiling oils fractionated from wood tar, saidscrubbing being performed in two stages and in the second stage thevapors being positively cooled to a limited extent.

49. In an apparatus for wood distillation, a, retort, a vapor receivingbell in free vapor connection with said retort and arranged to controlvapor pressure within the retort by varying the speed of withdrawal ofsaid vapors upon change of volume of its vapor contents, and anapparatus arranged for scrubbing vapors with a separately distilled taroil fraction.

50. In an apparatus for wood distillation a retort, a vapor conduit, avapor receiving bell in free vapor connection with said retort andarranged to control vapor pressure Within the retort by varying thespeed of withdrawal of said vapors upon change of volume of its vaporcontents, means for scrubbing vapors with a separatelv distilled tar oilfraction, means for passing vapors against a counter-current of alkali,a condenser and vapor conduits connecting the said elements in sequenceto variable suction means controlled by said belL,

51. In a wood distillation apparatus, the combination with a retort, apressure-regulating device in open communication with said retort, andmeans for cooling the vapors on their way from the retort to saidpressure regulating device, of means for fractionating tar 0115 fromtar, and means for scrubbing the vapors from the pressure-regulatingdevice with said fractionated tar oils, to remove tar and light oilsfrom said vapors.

52. In the art of wood distillation, the process which comprisesgenerating vapors in a retort at atmospheric pressure, positivelyprecooling said vapors, scrubbing with tar oils, passing the purifiedvapors through alkali to absorb acids, and condensing alcohol and waterfrom the residual neutral vapors.

53. In the art of wood distillation the process which comprisesdistilling wood in a retort, scrubbing the resultant vapors with taroils, absorbing the acid from the scrubbed vapors, condensing water andwood spirit together. from the vapors and positively controlling theoperative pressure throughout the series of process steps.

54. In the art of wood distillation the process which comprisesdistilling wood, collecting the pyroligneous vapors, removing theimpurities and the valuable constituents therefrom, and withdrawing theresidual gases at a variable rate so as to maintain constant pressure inthe various stages of the process, said rate of withdrawal beinpositively controlled by the fluctuating voIume of the crudepyroligneous vapors distilled from the wood.

55. In the art of wood distillation, an apparatus comprising a wooddistilling retort having a vapor exit, a conduit leading therefrom,pressure-regulatin means connected with said conduit an followed byscrubbing means and acid-absorbing means, means for condensing alcoholvapors, a valved conduit leading from said alcohol condensing means to asuction producing means adapted to operate at constant speed, the valvein said last named conduit being actuated through suitable connectingmem-.

bers by the said pressure-regulating means.

56. In a wood distilling apparatus, a. retort having a vapor outlet, acooling conduit, a vapor receiving and pressure-regulating device inopen connection with said vapor outlet, a vapor scrubbing device and aconduit from said scrubbing device connected with suction meansregulated independently of the pressure within said scrubbing device.

57. In the art of wood distillation the process which comprisesdistilling wood and HARRY O. OHUTE. Witnesses:

CLARENCE EDWARDS, Ross MEYERS.

